El Yunque, Puerto Rico
In about the time you'd spend watching a long baseball game, you could fly to San Juan, Puerto Rico, on a direct flight from Chicago, Newark, Atlanta, or Dallas; rent a car; and drive 20 miles east to El Yunque National Forest. Here is the rain forest next-door: a dense jungle with giant tree ferns, parrots, and boa constrictors.
There are no lodgings in the park, but camping is allowed with a permit. Or stay at the Rainforest Inn, where a two-bedroom villa runs $170 a night. The property has private trails in the forest and guides to lead you to remote waterfalls and swimming holes. After a couple of days exploring the jungle, drive 15 minutes to Luquillo Beach and surf in the warm Caribbean waters.